The hypothalamic-pituitary-adrenal (HPA) axis and its byproduct, cortisol, have been hypothesized to be the mediators that links chronic stress to adverse health outcomes, including increased obesity risk. This mediation is hypothesized to occur via several mechanisms, including stress-related cortisol secretion leading to both increased caloric consumption and a shift in preference to comfort foods (i.e., foods high in fat and/or added sugars). Under conditions of chronic stress, aberrations in the normal diurnal pattern of cortisol secretion occur, and obese, compared to non-obese, adults have been reported to demonstrate these aberrations more frequently. Although it is vital to understand the origins of these associations and the mechanisms through which they are established, few studies have examined links between HPA axis functioning and obesity in childhood. Furthermore, no studies have examined potential links between stress, cortisol, eating behavior, and obesity among low-income preschool children, though this population carries the greatest burden of the childhood obesity epidemic, and disparities in obesity prevalence emerge in this age range. This application, therefore, proposes 3 specific aims: Aim 1: To examine the association between diurnal cortisol patterns and weight status within a population of low-income preschool-aged children. Hypothesis 1: Children with alteration of the normal diurnal pattern of cortisol secretion will demonstrate a higher prevalence of obesity compared to children with the typical diurnal pattern. This alteration of the diurnal pattern will most commonly present as hypercortisolism, but may also present as hypocortisolism. Aim 2: To examine the association between diurnal cortisol patterns and eating behaviors within a population of low-income preschool-aged children. Hypothesis 2: Children with alteration of the normal diurnal pattern of cortisol secretion will demonstrate a higher prevalence of food-related tantrums, emotional eating, and eating in the absence of hunger compared to children with the typical diurnal pattern. Aim 3: To examine the association between diurnal cortisol patterns and dietary composition within a population of low-income preschool-aged children. Hypothesis 3: Children with alteration of the normal diurnal pattern of cortisol secretion will consume more comfort foods (foods high in fat and/or added sugars) compared to children with the typical diurnal pattern. PUBLIC HEALTH RELEVANCE: Childhood obesity is a significant public health problem, particularly for low-income populations. Obesity, once established in childhood, is very likely to track into adulthood. More effective approaches to preventing and treating childhood obesity are needed. A focus on the intersection of stress, eating behavior, and obesity may inform the development of more effective intervention and prevention programs.